Field of the Invention
Embodiments of the invention generally relate to a leadless heart stimulator, such as an intracardial or epicardial heart stimulator, which includes an activity sensor. In addition, embodiments of the invention generally relate to an activity sensor that detects physical activity based on detected acceleration values.
Description of the Related Art
Generally, implantable heart stimulators, such as cardiac pacemakers, have a housing, in which a battery is arranged, which allows operation of the pacemaker over many years. Typically, the battery supplies power to a pacemaker controller, which is generally connected to a detection stage for heart signals and also to a stimulation pulse generator. Generally, both the stimulation pulse generator and the detection stage for heart signals are in turn connected to connectors for one or more electrode leads, which make it possible to deliver stimulation pulses generated by the stimulation pulse generator to the muscle tissue of the heart (myocardium) or to detect and to process electrical potentials in the heart.
Cardiac pacemakers of this type are typically implanted beneath a patient's collarbone and with which a connection is made to the heart via flexible electrode leads, which end in the respective heart chamber (atrium or ventricle) and are provided there with electrodes. Generally, leadless cardiac pacemakers are also used, which may be placed as a whole in a heart chamber (intracardially). Typically, cardiac pacemakers may be secured externally on the heart (epicardially).
Generally, heart stimulators to be placed on or in the heart that do not require any electrode leads, are referred to as “leadless”. Within the scope of this invention, such cardiac pacemakers will therefore be referred to herein as leadless cardiac pacemakers or synonymously as heart stimulators having no electrode leads.
Typically, different operating modes and variants of cardiac pacemakers may be used and are not further explained herein. In particular, generally, a stimulation rate of a cardiac pacemaker is controlled depending on the metabolic need of a patient. Typically, rate-adaptive cardiac pacemakers of this type require a sensor for the metabolic need. Generally, possible sensor types are temperature sensors or acceleration sensors (accelerometers).
For example, U.S. Pat. No. 4,926,863, entitled “Rate Responsive Cardiac Pacemaker”, to Alt, appears to describe a rate-adaptive cardiac pacemaker that includes an acceleration sensor. U.S. Pat. No. 8,543,205 B2, entitled “Temperature Sensor for a Leadless Cardiac Pacemaker”, to Ostroff, appears to describe a rate-adaptive intracardial cardiac pacemaker that includes a temperature sensor. For example, U.S. Pat. No. 7,937,148 B2, entitled “Rate Responsive Leadless Cardiac Pacemaker”, to Jacobson, appears to describe a rate-adaptive intracardial cardiac pacemaker that includes an acceleration sensor.
U.S. Pat. No. 5,031,615, entitled “Rate Responsive Cardiac Pacemaker”, to Alt, appears to disclose a cardiac pacemaker that includes an accelerometer. For example, U.S. Pat. No. 5,215,084, entitled “Cardiac Pacemaker with Activity Sensor”, to Schaldach, appears to disclose a cardiac pacemaker that includes an activity sensor for detecting physical activity of a patient. U.S. Pat. No. 5,243,979, entitled “Method and Apparatus for Implementing Activity Sensing in a Pulse Generator”, to Stein et al., appears to disclose a cardiac pacemaker that includes a sensor responsive to the patient's metabolic demand. For example, U.S. Pat. No. 5,330,510, entitled “Pacemaker with Patient Effort-Controlled Frequency”, to Legay et al., appears to disclose a pacemaker with accelerometers wherein each of the accelerometers is sensitive in one direction of a Cartesian coordinate system.
U.S. Pat. No. 5,383,473, entitled “Rate-Responsive Implantable Stimulation Device Having a Miniature Hybrid-Mountable Accelerometer-Based Sensor and Method of Fabrication”, U.S. Pat. No. 5,425,750, entitled “Accelerometer-Based Multi-Axis Physical Activity Sensor for a Rate-Responsive Pacemaker and Method of Fabrication, and U.S. Pat. No. 5,833,713, entitled “Rate Responsive Pacemaker Having an Accelerometer-Based Physical Activity Sensor”, all to Moberg, appear to disclose a rate-responsive pacemaker with a physical activity sensor.
U.S. Pat. No. 5,480,412, entitled “System and Method for Deriving Hemodynamic Signals from a Cardiac Wall Motion Sensor”, to Mouchawar et al., appears to disclose a processing system and method for deriving an improved hemodynamic indicator from cardiac wall acceleration signals. U.S. Pat. No. 5,496,361, entitled “System and Method for Detecting Cardiac Arrhythmias Using a Cardiac Wall Acceleration Sensor Signal”, to Moberg et al., appears to disclose implantable leads incorporating accelerometer-based cardiac wall motion sensors. U.S. Pat. No. 7,937,148, entitled “Rate Responsive Leadless Cardiac Pacemaker”, to Jacobson, appears to disclose a pacemaker with an activity sensor.